The direct objective is the determination of wet brain weight, DNA/brain, and protein/brain of mice which were subjected separately or jointly to nutritional and environmental deprivation during a period corresponding to that during which most human functional mental retardation is believed to start. Comparison with brain parameters of control animals tells us if either deprivation or both together affect brain in overall size, brain cell number, or cell complexity. If any such biological effect is found, there is little likelihood of later rehabilitation, and this will be checked directly by running experiments out to an age beyond which there is little likelihood of rehabilitation because normal rodents show little or no change in brain parameters after that age. Our attack on this problem has several special features. First, we will use equalized litters which we have developed to reduce brain parameter variation by an order of magnitude over that existing in presently published methods. Second, we will study pre-weaning mice at ages comparable to those at which human deprivations generally work their damage. Third, our previous work showed how to use the existence of brain growth stages to increase the reliability of interspecies extrapolation. Fourth, since virtually all human disasters present both nutritional and environmental deprivation, we will concentrate our main efforts on measuring the consequences of giving those deprivation simulations simultaneously.